Optical plastic discs are a commonly used medium for storing large amounts of information. Optical plastic disc formats include such consumer products as laser discs, compact discs, and digital video discs (DVD).
A proven method of reproducing optical plastic discs is via injection molding. In order to reproduce optical plastic disc via injection molding, a very clean environment and precision equipment is necessary.
Typically, information from a premaster tape is first transferred to and stored on a glass master disc. The glass master disc has a series of microscopic pits and flat areas spiraling from the center of the disc. These pits and flat areas represent the information stored on the glass master disc which is to be reproduced on a metal disc called a "stamper.". The (positive) glass master disc is typically used to create (negative) stampers. The stamper is placed onto a set of mold dies. Mold dies consist of a male metal circular plate and a female metal circular plate, and they are polished to a mirror surface quality. These molds with a stamper create a shell into which molten plastic can be injected for production of optical plastic discs.
During the production process, it is essential to keep the inside surfaces of the mold dies very clean and free of dust and other contaminants, so an operator of an injection molding machine must thoroughly and carefully clean the inside surfaces of the molds whenever the machine is stopped for any reason. Conventional methods of cleaning the surface of a mold are time consuming. Currently, acetone is typically used as a cleaning agent. However, using acetone has several drawbacks including that it produces hazardous fumes and is toxic to humans. Also, currently, relatively expensive gauze-like cloth is used to wipe the molds in the cleaning process. However, when using such cloth, extra care must be taken and skill is required so as not to damage the surface of the mold.
Moreover, the density of the pits and surfaces which stores information on the optical plastic discs continues to increase as technology moves on. For example, the density of pits and surfaces of DVD discs are greater than that of compact discs. This increasing density means that the production process becomes more sensitive to contaminants on the mold dies.